Reproducing steps:
1. emacs -Q
2. open the shell file in attachment
3. M-x show-paren-mode
4. move cursor just before the char ‘\' in last line

It also happens with the emacs master.


In GNU Emacs 26.3.50 (build 1, x86_64-apple-darwin17.7.0, NS appkit-1561.61 Version 10.13.6 (Build 17G9016))
 of 2019-11-21 built on jundeMac
Repository revision: 3ee8ee8476fef2a5e8159f7597e36e0953295ce2
Windowing system distributor ‘Apple', version 10.3.1561
Recent messages:
For information about GNU Emacs and the GNU system, type C-h C-a.
Setting up indent for shell type bash
Indentation variables are now local.
Indentation setup for shell type bash

Configured using:
 ‘configure —with-ns '--enable-locallisppath=/Library/Application
 Support/Emacs/${version}/site-lisp:/Library/Application
 Support/Emacs/site-lisp’ --with-modules --disable-acl
 —without-makeinfo CFLAGS=-O2’

Configured features:
JPEG RSVG GLIB NOTIFY GNUTLS LIBXML2 ZLIB TOOLKIT_SCROLL_BARS NS MODULES
THREADS LCMS2

Important settings:
  value of $LANG: zh_CN.UTF-8
  locale-coding-system: utf-8-unix

Major mode: Shell-script

Minor modes in effect:
  sh-electric-here-document-mode: t
  ido-everywhere: t
  global-hl-line-mode: t
  tooltip-mode: t
  global-eldoc-mode: t
  electric-indent-mode: t
  mouse-wheel-mode: t
  tool-bar-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  blink-cursor-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  line-number-mode: t
  transient-mark-mode: t

Load-path shadows:
None found.

Features:
(shadow sort mail-extr emacsbug message rmc puny dired dired-loaddefs
format-spec rfc822 mml mml-sec epa derived epg gnus-util rmail
rmail-loaddefs mm-decode mm-bodies mm-encode mail-parse rfc2231
mailabbrev gmm-utils mailheader sendmail rfc2047 rfc2045 ietf-drums
mm-util mail-prsvr mail-utils sh-script smie executable package easymenu
epg-config url-handlers url-parse auth-source cl-seq eieio eieio-core
cl-macs eieio-loaddefs password-cache url-vars windmove ido seq byte-opt
gv bytecomp byte-compile cconv cl-loaddefs cl-lib display-line-numbers
hl-line elec-pair time-date china-util tooltip eldoc electric uniquify
ediff-hook vc-hooks lisp-float-type mwheel term/ns-win ns-win
ucs-normalize mule-util term/common-win tool-bar dnd fontset image
regexp-opt fringe tabulated-list replace newcomment text-mode elisp-mode
lisp-mode prog-mode register page menu-bar rfn-eshadow isearch timer
select scroll-bar mouse jit-lock font-lock syntax facemenu font-core
term/tty-colors frame cl-generic cham georgian utf-8-lang misc-lang
vietnamese tibetan thai tai-viet lao korean japanese eucjp-ms cp51932
hebrew greek romanian slovak czech european ethiopic indian cyrillic
chinese composite charscript charprop case-table epa-hook jka-cmpr-hook
help simple abbrev obarray minibuffer cl-preloaded nadvice loaddefs
button faces cus-face macroexp files text-properties overlay sha1 md5
base64 format env code-pages mule custom widget hashtable-print-readable
backquote threads kqueue cocoa ns lcms2 multi-tty make-network-process
emacs)

Memory information:
((conses 16 225954 6854)
 (symbols 48 21886 0)
 (miscs 40 555 199)
 (strings 32 37144 2102)
 (string-bytes 1 980109)
 (vectors 16 38848)
 (vector-slots 8 826341 2164)
 (floats 8 56 60)
 (intervals 56 264 0)
 (buffers 992 12))